. This is a revised application for a Mentored Research Scientist Development Award in Aging. The applicant has a background in exercise and applied physiology and research experience in the examination of changes in skeletal muscle due to inactivity and training. He has made a decision to devote his academic career to examining aging and age related issue. This proposal describes the applicants training plan in a department of geriatrics and a research project to examine the effects of two different types of muscle contractions on muscle protein metabolism and muscle strength and power in older women and men. Lengthening muscle actions are known as eccentric contractions and have been shown to result in skeletal muscle damage, delayed onset muscle soreness, and a cascade of metabolic events that result in repair of the damage, which may stimulate the hypertrophic response to resistance training. The laboratory of Dr. William Evans, the primary sponsor of the applicant, has previously described the stereotypical acute phase response to eccentric exercise and the resultant changes in whole body protein metabolism. The applicant proposes to test the hypotheses that eccentrically biased exercise will lead to greater increases in the rate of muscle protein degradation and synthesis, net protein balance, growth factor levels, inflammatory response, and ubiquitin levels, than does concentrically biased exercise performed at a similar intensity. In addition, he proposes that because of these differences, eccentrically biased exercise training will lead to a greater muscle hypertrophy, and muscle strength and power than concentrically biased exercise. He plans on subjects performing only eccentric or only concentric resistance exercise training in order to examine adaptive changes that occur in senescent human skeletal muscle as a result of these two different types of muscle actions. This examination of the metabolic adaptations to concentric and eccentric exercise is intended to increase knowledge of the adaptive mechanisms of skeletal muscle in older individuals and further understanding of how resistance exercise training effects muscle protein metabolism. Given the effects of resistance training on senescent muscle and the importance of eccentric actions in daily activities, the proposed study is considered by the applicant as having impact on developing interventions for improving functional status in older persons.